GB2160855A - Apparatus and method for treating fluids - Google Patents

Abstract

A method is provided for treating industrial fluids, such as water effluents and slurries to assist in preventing formation of scale or fouling of industrial plant or to assist in avoiding their adverse environmental effects and in reducing the tendency for particulate material to settle out. The method comprises producing a laminar flow of the industrial fluid in a conduit; accelerating the laminar flow of industrial fluid; and applying a magnetic field to the accelerated flow of industrial fluid transverse to the direction of flow of the fluid, wherein the product of the velocity of the accelerated industrial fluid (in metres per second) and the magnetic field strength (in Tesla) is at least 8.

Description

SPECIFICATION Apparatus for and method of treating fluids The present invention relates to an apparatus for and method of treating fluids, such as water and industrial heating fluids, effluents and slurries.

Water treated by the apparatus or method of the present invention may be used in the irrigation of plants, whereby plant growth is enhanced, or in the control of industrial plant or pipe scaling.

The apparatus and method of the present invention may also be used to treat industrial heating fluids, industrial effluents and slurries to prevent scale formation in or remove scale formed on industrial plant and to prevent fouling by particulate matter settling out of the fluid.

It is known that, although water is essential for plant growth, it is possible to inhibit plant growth by applying to much water to them. Many factors may contribute to the deleterious effects of overwatering of plants. It is belived that the following factors are of particular importance.

Water generally contains a substantial amount of mineral matter, normally in the form of salts dissolved out of the rocks through which the water either percolates into a well or flows from the source. When the water is applied to or around a plant, the water evaporates or is absorbed, leaving the mineral matter deposited on the plant or on the earth around it. The mineral matter on the plant may interfere with the plant's metabolism and therefore have a deleterious effect on it.

The mineral matter on the earth may cause the earth to become less porous, thus making it difficult for water to penetrate into the earth to the roots of the plant. It is known that most of a plant's water is absorbed through its roots and therefore if the water cannot penetrate to the roots the plant will be adversely affected, even if there is a pool of water on the surface of the earth around it.

In general water is acidic, either due to the presence of minerals in the water or due to the emissions from the combustion of fossil fuels, which are absorbed into atmospheric water vapour and precipitated as 'acid rain'. A large number of plants are adversely affected by acid water and therefore application of large quantities of acid water, either by irrigation or by rainfall, will have deleterious effect on these plants.

It has been observed that plants, even if they have been subject to overwatering, generally appear to improve in condition after they have been watered by rain falling during a thunderstorm, even though they do not appear to show the same improvement in condition after they have been watered by water from the mains or an irrigation supply.

Investigations have been carried out in order to discover the reason why plant growth is enhanced by rain falling during a thunderstorm, but not so much by water containing dissolved minerals, and to find a way in which the effect may be stimulated in the absence of a thunderstorm.

It is accordingly a first object of the present invention to provide an apparatus for and method of treating water to make the water more suitable for irrigating plants and to use the treated water to irrigate plants thereby to enhance their growth.

It is also known that when water is used in industrial processes, for instance as a fluid in a heat exchanger, there is a tendency for scale to form on the inside surfaces of the pipe-work or the heat-exchanger. It is belived that scale formation occurs due to a concentration of the salts present in the water adjacent these surfaces. The most common salts found in water for such uses are suphates, phosphates and carbonates, generally of alkali or alkaline earth metals. Where these salts are more soluble in cold water than hot water, the concentrated salt adjacent these surfaces, which will generally be hotter than the water flowing past them, will crystallise out, and the salt crystals will cling to the surfaces, thus forming the scale.This mechanism can be seen operating for instance in an electric kettle wherein there is a tendency for calcium carbonate scales to form on the heating element.

The formation of scale in pipe-work and heat exchangers costs industry hundred of millions of pounds a year. While the scale is present, especially in heat exchangers, the energy costs of a process will rise due to the heat insulation effect of the scale. This will reduce the efficiency of the heat exchange process.

Eventually, it will become necessary to remove the scale. This may, in some cases, be achieved by pumping dilute solutions of acids or alkalies as cleaning agents, through the pipe work and heat exchangers. This clearly involves the use of an additional reagent, which adds to the expense of the process.

However, in some cases, the scale cannot be removed by cleaning agents, and it is therefore necessary to strip down the pipe-work and heat exchangers.

These may then be cleaned by rodding out, by strong acid treatment, or by use of high pressure water jets. Such cleaning is obviously very labour intensive and therefore expensive, and may also be very damaging to the pipes work itself.

Moreover, during either type of cleaning operation it is necessary to shut down the industrial plant, thus adding the cost of lost production to the cost of the cleaning operation.

The prblem of scale formation also occurs in the treatment of industrial effluents, for instance phosphoric acid streams from fertilizer production. Such effluents are commonly also corrosive, making it necessary to replace pipe-work more frequently than is economically desirable. Moreover, such effluents must be carefully disposed of in order to prevent adverse environmental effects.

It is accordingly a second object of the present invention to provide an apparatus for and method of treating water and industrial fluids and efflents to assist in preventing formation of scale in and in removing scale from pipe-work and heat exchangers in industrial plant, and to reduce the corrosive and environmentally adverse effects of such effluents.

It is further known that when treating industrial slurries, for instance in tin or gold mining industries, there is a tendency for the solid material in the slurry to settle out, causing fouling of the pipework or channels in which it is flowing.

Accordingly, it is a third object of the present invention to provide an apparatus for and method of treating slurries to reduce the tendency of the solid material in the slurry to settle out.

It is also common to filter such industrial slurries to remove the slurry particles from the fluid. However, the time needed to carry out the filtration is generally quite long and also the filter can readily become fouled by the particles.

It is therefore a fourth object of the invention to provide an apparatus for altering the morphology of suspended slurry particles to improve the filtration characteristics of the slurry and to reduce the time required for filtration. This will increase the operational period of a filtration plant.

According to a first aspect of the present invention, there is provided an apparatus for treating fluids comprising: a closed fluid conduit; a flow straightner for producing a laminar flow of fluid downstream thereof in the conduit; a venturi device downstream of the flow straightner for accelerating the laminar flow of fluid; and means for applying to the accelerated flow of fluid a magnetic field, transverse to the direction of flow of the fluid, located within said conduit, wherein the product of the velocity of the accelerated fluid (in metres per second) and the magnetic field strength (in Tesla) is at least 8.

According to a second aspect of the present invention, there is provided a method of treating fluids comprising: producing a laminar flow of fluid in a conduit; accelerating the laminar flow of fluid; and applying a magnetic field to the accelerated flow of fluid transverse to the direction of flow of the fluid; wherein the product of the velocity of the accelerated fluid (in metres per second) and the magnetic field strength (in Tesla) is at least 8.

The fluid may be conveyed from the conduit in an open channel, such as a gutter or irrigation channel, but is preferably conveyed from the conduit in a closed pipe.

The conduit and pipe are preferably circular in cross-section and may be made from non-magnetic, for instance plastics, materials.

In general fluid pumps are of the centrifugal type and impart to the fluid pumped out of it a swirling motion such that as the fluid travels along the conduit it follows a spiral path. If such a pump is used, it will be necessary to provide a separate flow straightener (which is also known as a laminar flow divider). These are known in the art.

A preferred form of laminar flow divider for small cross-section conduits comprises a rigid bar or plate set at right angles to the flow of fluid through the venturi device. The bar or plate may be, for instance, a plastics extrusion.

A preferred form of laminar flow divider for larger cross- section conduits comprises one or more elongated members having a cross-shaped or parallel cross-section which divides the flow of water in the conduit into four equal parts and prevents flow of water through the centre of the conduit. The flow divider may be made from two or more interesting plates or formed as a single piece of material, for instance in the form of a plastics extrusion.

Advantageously the flow divider produces a laminar flow in which the velocity distribution in the direction transverse to the flow direction is uniform.

Alternatively, the flow straightener may comprise a positive displacement pump which will generally cause the water it is pumping to flow in laminar fashion, or may assist such a positive displacement pump in providing such a laminar flow.

The flow straightener may also comprise the conduit itself, especially where the conduit is a pipe. It is known that, even if the pump imparts a swirling motion to the water, after travelling a certain distance, the water begins to flow in a laminar fashion. The disadvantage of this is that the velocity distribution is very uneven, the water at the centre of pipe travelling considerably faster than the water at the edge of the pipe. Generally, there is a layer of water at the edge of the pipe which is hardly moving at all due to the frictional effects of the pipe.

It will be appreciated that the use of the conduit as a flow straightener or the use of a flow straightener in the pipe may reduce the velocity of the flow of fluid to such an extent that it can no longer be suitably accelerated for treatment by the magnetic field. A skilled person will therefore appreciate that the fluid should be pumped at such a rate that its velocity after passing the flow straightener is sufficient for it to be suitably accelerated.

Venturi devices for accelerating a flow of water/ or any other fluid are known in the art and any of these may be used.

A venturi device operates by reducing the crosssectional area of the conduit so that the fluid flowing in the conduit has to travel faster through this region in order to maintain the same volume flow through the pipe. Thus the venturi device may be formed by reducing the diameter of the pipe or by inserting a member in the pipe to obstruct part of it.

The means for applying a magnetic field preferably comprises at least one pair of permanent magnets fixed such that a north pole of one magnet is held in spaced apart relationship with the south pole of the other. Conveniently there are at least two pairs of magnets, and in larger cross-section conduits, there may be a larger number of pairs of magnets.

Alternatively the field may be applied elecromagnetically for instance by use of a least one magnetic coil. The coil may be supplied directly from a DC source or from an AC source via rectifier circuit, for instance a diode rectifier circuit. Preferably the or each coil is located around a bar of magne tisable material.

Advantageously, magnetic pole pieces held on the bars or permanent magnets, located in the conduit, and shaped to act as the venturi device are used.

The bars or permanent magnets may be located either co-axially with the conduit or transversely of the conduit. In the former case, the bars or magnets may also be configured to act as the flow straightener, the venturi device or both.

In a preferred embodiment, wherein the flow straightener is a cross-shaped member, the means for applying the magnetic field may comprise four quadrant shaped magnetic pole pieces held in spaced apart relationship to define therebetween a flow channel having a cross-shaped cross-section, the flow channel being offset at about 45 to the flow straightener and the poles being alternately north and south poles.

Advantageously, there are two means for applying magnetic fields to the accelerated flow of water. In a preferred embodiment, each means comprises a four quadrant structure as set out above and the north and south poles in one structure are connected by a bar magnet, which may be a permanent magnet or bar of magnetisable mate rial surrounded by af coil, to a south or north re- spectively pole in the other structure. Preferably each bar magnet is circular in cross-section, although bar magnets of for instance rectangular, hexagonal or octagonal, cross-section may also be used.

Conveniently a second flow straightener is located in the conduit downstream of the or each means for applying the magetic field.

Advantageously, where permanent magnets are used, they are held spaced apart relationship by being fixed onto the flow straightener(s).

Preferably, the magnetic field strength of the means for applying the magnetic field is about 1.25 Tesla and the accelerated water has a velocity of about 9 metres per second. However, it will be possible to vary these values as necessary as long as the product of them does not fall below the value given above.

Advantageously, the conduit is in two parts, preferably of equal length, and is coupled together around the remaining parts of the apparatus, for instance by use of co-operating flanges on one end of each part and bolts passing through the flanges.

However, it will be clear to a person skilled in the art that other types of coupling could be used to the same effect.

Preferably the remaining parts of the apparatus are removably mounted in the two-part conduit.

For instance, a retainer ring may be fixed into each part of the conduit. Alternatively, there may be step formed in each part of the conduit, so that the end of each part adjacent the coupling is wider than the other end of each part. The ends of the remaining part of the apparatus will be arranged to abut against the rings or the steps when the apparatus is assembled. The apparatus may also include means for preventing the remaining parts thereof rotating in the conduit. For instance, a key may be provided longitudinally on the inside wall of each part of the conduit for engagement with a co-operating keyway formed on the remaining parts of the apparatus.

Preferably, the inside of the conduit and the parts of the apparatus are treated to enable them to withstand the corrosive or abrasive effects of any fluid flowing therethrough. For instance the apparatus may be coated with polytetrafluoroethylene (PTFE) to reduce abrasion and drag effects, or an acid or alkali resistant resin to prevent corrosion. Where the conduit is provided in two parts, it will be possible to renew the coating at regular intervals without disrupting significantly the operation of the apparatus.

A third aspect of the invention comprises the use of water treated in the apparatus or by the method described in the irrigation of plants, whereby plant growth is enhanced.

It is believed that the following theory can be used to explain why water treated in the apparatus or by the method of the present invention enhances plant growth. However, it is not wished that the invention, the scope of which is set out in the claims appended hereto, should be limited to this theory.

It is believed that rain falling during a thunderstorm enhances plant growth because its properties have been altered by the efect of the static electricity discharges, in the form of lightning, which occur during thunderstorms. It is believed that the treatment of water according to the invention mimics the effects of these static electricity discharges.

Water, especially if it contains mineral matter in ionised form, is a conductor of electricity. It is known that if a conductor is moved across a magnetic field an electric current is induced in the conductor. Thus, as the water flows through the magnetic field, it is believed that a current is induced therein and that this current affects the properties of the water in a similar manner to the effects of the static electricity discharges on rainfall.

It is believed that the effect of the magnetic field on the water changes the ionisation state of the water, marginally increases its pH and affects the way in which the mineral matter in the water crystallises. These changes enable the water to be more easily absorbed by the plant, assist in preventing the build up of mineral matter on the plant, and cause the mineral matter to be deposited on the ground in such a matter that it does not prevent the water from reaching the roots of the plant to the same extent that untreated water does.

Moreover, it is believed that the surface tension properties of the water are affected such that the water is able more easily to penetrate the ground and reach the roots of the plants. The treatment of the water therefore reduces the deleterious effects of watering.

A fourth aspect of the invention comprises treating industrial fluids, such as water, effluents and slurries in the apparatus or by the method described above, to assist in preventing formation of scale or fouling on and in removing scale or fouling from industrial plant, such as heat exchangers and pipework.

The present invention also includes a method of treating industrial effluents and slurries to assist in avoiding their adverse environmental effects and to reduce the tendency for particulate material to settle out by use of the apparatus or method described above.

It is believed that the apparatus and method, as applied to industrial fluids, effluents and slurries, has the following effect, although it is not intended that the invention should be limited to this explanation.

It is believed that in such industrial fluids, effluents and slurries as desribed above, there will still be a tendency for salts in the fluids or slurries to concentrate and crystallise. However, it is believed that treatment according to the invention places the crystals or slurry particles in an electrostatically charged metastable state in which state the tendency for them to stick together and thus form scale or fouling is significantly reduced. The crystals or slurry particles thus remain in suspension and reduce the amount of scale or fouling formed.

Moreover, since the fluid contains suspended crystals or slurry particles, it will be somewhat abrasive and will therefore be able to remove existing scale or fouling by abrasion.

It can thus be seen that the use of the present invention in industrial processes will significanly reduce the amount of time and money which needs to be spent to combat the effects of scale and fouling formation.

It is belived that in the meta stable state induced by the treatment according to the present invention, the corrosive and adverse environmental effects of industrial effluents are reduced, thus making it easier to dispose of them.

A number of embodiments of apparatus accord ing to the present invention are now described, by way of example only, with reference to the accom panying drawings, in which: Figure 1 is a side view of a first embodiment of the apparatus with parts cut away for the sake of clarity, Figure 2 is a view along line 2-2 of Figure 1; Figure 3 is a similar view to Figure 1 of a second embodiment of the apparatus with electrical con nections shown schematically; Figure 4 shows a sectional side view of a third embodiment of the apparatus; Figure 5 is a view along arrow X of Figure 4; Figure 6 is a similar view to that shown in Figure 5 of a fourth embodiment of the apparatus; Figure 7 is a similar view to that shown in Figure 5 of a fifth embodiment of the apparatus; Figure 8 is a similar view to that shown in Figure 5 of a sixth embodiment of the apparatus; and Figure 9 is a sectional side view of the apparatus of Figure 8.

Referring now to Figures 1 and 2 of the draw ings, the first embodiment of the apparatus com prises a pipe (10) which is connected to a pump (not shown) for driving water from left to right as shown in Figure 1.

A first flow divider (12), comprising a pair of intersecting plates (14,16) is located in the pipe (10) and is fixed in position by welding to the pipe (10).

Each plate (14,16) has in it a slot extending half way along the centre line from one end for co-operation with the slot on the other plate. The flow divider (12) has a cross-shaped cross-section and is constructed of non- magnetic stainless steel.

A quadrant shaped pole piece (18,20,22,24) of magnetic material, such as iron, is welded onto the downstream end of each of the arms of the flow divider (12). The poles (18,22,24) are fixed onto the flow divider (12) by means of slots and are held in spaced apart relationship so as to define a crossshaped flow channel (26) therebetween.

A well (28,30,32,34) is formed in the face of each of the poles (18,20,22,24 respectively) away from the flow divider (12) and has fixed therein one end of a rod shaped permanent magnet (38,40,42,44 respectively).

The poles (18 and 22) are south poles and the ends of the permanent magnets (38 and 42) respectively therein are also south poles. The poles (20 and 24) and end of magnets (40 and 44) therein are north poles. The poles are therefore of opposite polarity to those immediately adjacent each other. Thus a magnetic field is created across each arm of the flow channel (26) between adjacent north and south poles.

The magnets have a field strength of 1.25 Tesla which produces a field in the venturi (see below) of about 0.125 Tesla.

The cross-shaped flow channel (26) is of considerably smaller cross-sectional area than the pipe (10) and therefore acts as a venturi device for accelerating water flowing in the pipe (10).

The end of the permanent magnets (38,40,42,44) remote from the flow divider (12) are located in wells in further quadrants which in turn are held in spaced apart relationship by being welded onto a second flow divider (46) in the same manner as described above. The second flow divider (46) is also welded onto the pipe (10). Thus the parts disposed in the pipe are symmetrical about a plane bisecting the permanent magnets (38,40,42,44) except that the poles at opposite ends of the permanent magnets must, of necessity have opposite polarities.

Referring now to Figure 3, there is shown a second embodiment of the apparatus which is smaller in construction to the apparatus shown in Figures 1 and 2. Like parts have therefore been given like reference numerals.

However, the magnetic pole pieces (18,20,22,24) are connected to the pole pieces attached to the second flow divider by bars (58,60,62,64) of magnetic material surrounded by coils (68,70,72,74).

The coils are connected to a DC supply of electricity (78) as shown such that bars 58 and 62 are magnetised in the opposite direction to bars 60 and 64 when current is passed through the coils.

The power supply circuit includes a rheostat 76 so that the current supplied to the coils can be varied as necessary to effect treatment of the water.

In use of either of these embodiments, the pump forces water from let to right in the tube. It is assumed that the water arriving at the upstream end of the first flow divider (12) is flowing turbulently.

As it encounters the flow divider (12) the water is constrained to flow in laminar manner. At the downstream end of the flow divider (12) the water flowing in laminar fashion encounters the poles (18,20,22,24) which act as a venturi device and accelerate the water into the flow channel 26. As the accelerated water passes through the flow channel 26 the poles (18,20,22,24) will exert a magnetic field transverse to the direction of flow of the water and will induce a current therein.

On exiting from the flow channel 26 the water decelerates and passes parallel to the magnets (38,40,42,44) to the second set of poles. The water is then reaccelerated and again passes through a magnetic field transverse to the direction of water flow.

The water then flows past the second flow divider which maintains the laminar flow of water past the magnets.

In a typical example of the operation of the method, the water is pumped originally at a velocity of less than 2 metres per second, but is accelerated by the venturi effect of the poles to a velocity of about 9 metres per second.

The produce of the field strength (in Teslas) and the velocity of the accelerated flow of water is therefore 11. It will be appreciated that this value is only typical and lower or higher values may be used provided that the value is at least 8.

The water exiting from the pipe is used to irrigate plants in order to enhance their growth. On a trial plot using a sample of 10,000 plants, it has been shown that plants irrigated with water which has been treated according to the present invention increase their weight over a given period by at least 10% and in some cases up to 17%, more than plants raised in conventional manner.

Referring now to Figures 4 and 5, there is shown a third embodiment of the apparatus, comprising a conduit (100) formed in two parts (100a and 100b).

At the adjacent ends of the two parts are formed co-operating flanges (102,104) which are held together by bolts (not shown). A retaining ring (106 or 108) is fixed inside each part of the conduit (100) at a distance from the flanges (102,104). A pair of diametrically opposed longitudinally extending keys (110,112) are fixed onto the inside wall of each part of the conduit (100).

A bobbin (114) is removably located in the conduit (100). The bobbin (114) comprises at each end two outer pole pieces (116,118) of particular crosssection and an inner pole piece (120) of generally rectangular cross-section. The pole pieces (116,118,120) are held in spaced apart relationship to form flow channels (122,124) therebetween by being welded onto flow divider bar (126). The pole pieces (116,118,120) have wells therein for fixedly receiving cylindrical or other shaped bar magnets (128) arranged with opposite poles adjacent one another as hown in Figure 5.

The opposite ends of the bar magnets (128) are fixed in wells in similar poles pieces at the other end of the bobbin.

Keyways are formed in outer surfaces of the outer pole pieces for co-operation with the keys on the parts of the conduits.

To assemble the apparatus, the two parts (110a,110b) of the conduit are separated and the bobbin (114) is inserted into one part (100a) thereof with the keys (110,112) engaged in the keyways and is pushed in until the pole pieces abut the retaining ring. The other part (100b) of the conduit is then inserted over the protruding end of the bobbin (114) with the keys (110,112) engaging the keyways and is pushed on until the flanges (102,104) abut one another. At this stage the other retaining ring will also be abutting the other pole pieces. The flanges are then bolted together.

Once assembled, the bobbin (114) cannot move to any significant degree in the conduit (100). In the assembled apparatus, the bars (126) act as flow dividers and constrain fluid to flow in laminar fashion through the conduit (100). The effect of the flow dividers (126) is enhanced by the pole pieces (116,118,120) and bar magnets (128), which also act as flow straighteners and as the venturi device.

This apparatus is particularly suitable for treating industrial fluids, effluents, and slurries, as the inside of the conduit (100) and the components of the bobbin (114) can be treated to prevent or reduce abrasion and corrosion damage.

The apparatuses shown in Figures 6 and 7 to which reference is now made are similar in construction to that shown in Figures 4 and 5, but are designed for larger and smaller conduits respectively. In the embodiment shown in Figure 6, there are four pole pieces at each end and twenty bar magnets, whereas in the embodiment of Figure 7 there are only two pole pieces at each end and two bar magnets. In the latter embodiment, the pole pieces act as both the flow straightener and the venturi, there not being sufficient surface area presented by the bar magnets for this purpose. Both these apparatuses comprises a flanged two part conduit and a removable bobbin and are coated for abrasion and corrosion resistance.

The apparatuses shown in Figures 4 to 7 all operate in similar manner. The dimensions of the flow spaces between the pole pieces and the magnets are designed to ensure that fluid flowing through them is accelerated to a flow rate of at least 9 metres per second. The magnets have such a strength that the field strength across each flow space is at least 0.125 Tesla.

If desired in all these embodiments, small nonmagnetic spacers may be arranged between the pole pieces to keep them in the desired orientation.

The apparatus shown in Figures 8 and 9 comprises a square cross- section conduit (200) having a number of square cross-section bar magnets (202) located transversely of the direction of flow in the conduit (200). The magnets are arranged with opposite poles adjacent one another and are spaced from one another by such a distance that they can act as both flow straighteners and as ven turi devices. The magnets are arranged in three successive sets so that fluids are treated three times during their flow through the conduit.

The top (204) of the conduit is removable and the magnets (202) are located in grooves (206) formed in the sides of the conduit (200). They are held in spaced apart relationship by non-magnetic spacers (208). The megnets (202) may therefore be removed to allow them and the inside of the conduit to be coated for abrasion and corrosion resistance.

The magnets are arranged so that as fluid flows through each set it is accelerated to about 9 metres per second and have a field strength of 1.25 Tesla.

The apparatuses of Figures 4 to 9 are of especial use in industrial processes. For instance, it has been shown that the use of one of these apparatuses in treating water for use in industrial heat exchangers has reduced the amount of scale found in the heat exchanger considerably, without the need for any chemical cleaning, rodding out or high pressure water jet cleaning.

It has also been found that phosphoric acid fouling in a fertilizer factory can be rendered more easy to control by passing it through such an apparatus.

Moreover, it has been found that treating slurries for filtration using these apparatuses improves the filtration characteristics of the slurries and reduces the time required for filtration.

It can therefore be seen that the present invention provide a significant advance in the treatment of fluids of all kinds, for instance for plant irrigation or in industrial use.

Moreover, it is envisaged that the treatment of the present invention may also be of use in improving the properties of other fluids, such as drinking water or slurries for waste disposal or fertilizing.

Claims (11)

1. A method of treating industrial fluids, such as water effluents and slurries to assist in preventing formation of scale or fouling of industrial plant or to assist in avoiding their adverse environmental effects and in reducing the tendency for particulate material to settle out, the method comprising: producing a laminar flow of the industrial fluid in a conduit; accelerating the laminar flow of industrial fluid; and applying a magnetic field to the accelerated flow of industrial fluid transverse to the direction of flow of the fluid, wherein the product of the velocity of the accelerated industrial fluid (in metres per second) and the magnetic field strength (in Tesla) is at least 8.

2. The method of claim 1, wherein the conduit is a closed pipe.

3. The method of claim 1 or claim 2, wherein the laminar flow in the industrial fluid is produced by use of a positive displacement pump.

4. The method of any one of claims 1 to 3, wherein the laminar flow in the industrial fluid is produced by use of a flow straightener.

5. The method of claim 4, wherein the flow straightener has a cross-shaped cross section as seen in the direction of fluid flow.

6. The method of claim 5, wherein the velocity distribution in the direction transverse to the fluid flow direction is uniform in the laminar flow.

7. The method of any one of claims 1 to 6, wherein the laminar flow is accelerated by use of a venturi device.

8. The method of any one of claims 1 to 7, wherein the magnetic field is applied by a pair of permanent magnets.

9. The method of any one of claims 1 to 7, wherein the magnetic field is applied electromagnetically.

10. The method of any one of claims 1 to 9, wherein a second magnetic field is applied to the accelerated flow of industrial fluid transverse to its direction of flow.

11. The method of any one of claim 1 to 10, wherein laminar flow is produced in the flow of industrial fluid immediately downstream of the magnetic field or fields.